The "correct" thing is less important than starting. Take a fraction of your account that you are willing to transfer, and transfer it. Move it to a bank/brokerage where you can buy ETFs or mutual funds, and make a purchase. Knowing you will do that, pick the amount you're most likely to follow through with.
An imperfect start is better than a perfect but unused plan. That even extends to which mutual fund you pick. Even a bad mutual fund beats cash over most time frames. So... start!